A Hadamard gate on one qubit followed by a CNOT gate is the standard recipe for building maximal entanglement. This simulator steps through that exact circuit, tracking the full two-qubit state at every stage, and lets you measure the finished entangled pair to see the correlation for yourself.
• A three-step circuit walkthrough: initial |00>, after Hadamard on qubit A, after CNOT(A to B). • Live probability bars for all four two-qubit outcomes (|00>, |01>, |10>, |11>) at each step. • Forward, backward and reset step controls. • A measurement button that only produces correlated results once the true Bell state (step 2) is reached. • Explicit state-equation labels describing what each step's quantum state actually is.
• Step to stage 1 (after Hadamard only) and note qubit A is now superposed but qubit B is still definitely |0> — no entanglement yet. • Step to stage 2 (after CNOT) and see the state become (|00>+|11>)/sqrt(2), with |01> and |10> both at 0%. • Measure the pair repeatedly (using reset and re-stepping) and confirm the two qubits' results always match — both 0 or both 1, never mixed.
This two-gate sequence is the standard building block for producing entanglement on real quantum hardware and appears as a subroutine inside larger algorithms, quantum error-correction codes, and quantum communication protocols. The Quantum Teleportation lab uses exactly this recipe as its starting resource — the shared Bell pair that lets Alice and Bob transmit a qubit's state using only entanglement and two classical bits.
A Bell state is one of four maximally entangled two-qubit states. The one built in this lab is (|00> + |11>)/sqrt(2): measuring either qubit gives a 50/50 random result, but the two qubits' results are always perfectly correlated with each other.
The Hadamard gate first puts qubit A into an equal superposition of |0> and |1>. The CNOT gate then uses that superposed qubit as its control, so the resulting flip on qubit B happens in superposition too — linking the two qubits into the entangled (|00>+|11>)/sqrt(2) state rather than a simple product state.
Before the CNOT gate is applied, qubit A and qubit B are still independent (unentangled), so measuring A only affects A — B's outcome is unrelated. Correlated results only appear once the full circuit reaches the actual Bell state, which is why this lab requires reaching step 2 (after CNOT) before allowing a measurement.
No. The correlation is real, but it cannot be used to send a message, because the outcome of measuring A is genuinely random — there is no way to control what value B will show. Observers only discover the correlation exists once they compare their results afterward, over an ordinary classical channel.